Tyler Bates
New member
Probabley a stupid question,but something I dont understand so guess its not too stupid but I started reading the atlas t-case post and dont understand the ratio their I get axle ratio but what the heck is t-case ratio
Transfer case gear ?
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Robert_Stephens
New member
More specifically, our Jeeps from the factory have a two speed transfercase (TC, as we slang it here as a metaphor), and in that it works this way;
You drive around in 2 wheel drive mode for the paved streets/highways. Only the rear wheels are powered. (2x4)
You shift the Jeep into 4 wheel drive, high range (4X4) and both axles are now powered, but the gear ratio is still as you were in 2x4, which is 1:1 ratio.
Now, you get into rough country and want to really have more power, more control, and go much much slower, and you then shift the TC into 4x4 "low" range. Many Jeeps have all sorts of ratios and this depends on the differential gearing.
For me and VEX, my own Jeep, I have 4.10 geared rearends (differentials). I also have a very very low 4 speed transmission with a compound low first gear, as it is called, and that is 7.71:1.
Then, in my TC, I have a kit installed that makes my "low range" 4:1 instead of the more typical 2+ something to 1. This makes for extreme low crawling and control and power to the four wheels.
Now, what I am investigating is putting in an Atlas TC, that has "3" speeds instead of 2. And in that, the lowest gear ratio is a whopping 10:1.
Hope that is helpful and more clear. If not, ask away more questions so you are comfortable with the data and expressions and terms.
Thanks, and no question is "stupid" here. We all learn as we go--even me, after 46 years of Jeepin'.
Robert
Also when you read the numbers, 2.72:1 for example which is the low gear ratio in a NP 231 TC, this is read as a reduction ratio,between the input and output shafts. soo when you are in 2 or 4 Hi you are 1:1.. so for every 1 revolution of the input shaft, you will net 1 revolution on the out put shaft. now once you pull the lever back to 4wd Low, you reduction ratio is 2.72:1 so for every 2.72 revolutions of the input shaft, there is a reduction to 1 revolution of the out put shaft.
the only real world example I can think of would be is you ride a mountain bike and start going up a hill, you change the gearing from a fast gear to one that assists you to get up the hill, you pedal more but your tire has less revolutions, enhancing your ability to get up the hill with less strain on the motor (you)
the only real world example I can think of would be is you ride a mountain bike and start going up a hill, you change the gearing from a fast gear to one that assists you to get up the hill, you pedal more but your tire has less revolutions, enhancing your ability to get up the hill with less strain on the motor (you)
Tyler Bates
New member
O ok that makes since so can you get a gear reduction kit for most all tc because that would probabley help my 4 banger
Robert_Stephens
New member
In your 1990 Wrangler with a 4 banger and running those large 35s, absolutely. The lower the better. A 4:1 would help you off road. No help on road however in 4x2.
Robert
Tyler Bates
New member
And that would work great for me because I dont drive it on road much at all if I do its to work which is only 1 mile but mostly its a weekend toy that I do all the ork to myself and can figure most of it out considering Im a mechanic for a living but doesnt mean I wont have questions which makes me appreciate all you guys
Robert_Stephens
New member
That's a good point. And so in your case, a 4:1 would be perfect and no need to go more extreme. For VEX, I have to get right down there so am looking at a Atlas for me. I am concerned in my case, and am investigating, if it hangs lower than the Dana 300. Mine is a DD big time and also has to go in very very bad places for prolong periods.
Robert
Small point of correction, the AX 5 is the same trans used in various toyota applications including behind 22r and 22re motors (more over seas than here in US), the 1st gear in those transmissions is deeper than that found in the AX5 in YJ's and TJ's. There is documented proof that you can swap the 1st gear and get a lower ratio. (over on the other forum it was detailed) I have not done this mod since I personally would never put the money or any effort at all into a AX5, plus I think you don't gain a whole lot more.
Robert_Stephens
New member
Ah, I see. I would not know as I have a T-18 and the Dana 300 TC. Interesting though.
Thank you,
Robert
Thank you,
Robert
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